There have been known medical image acquisition apparatuses, such as Magnetic Resonance Imaging (hereinafter, referred to as MRI) apparatuses, CT (Computed Tomography) apparatuses, and ultrasonic diagnostic equipment which are adapted for non-invasive acquisition of anatomic tomographic images of human body. According to these apparatuses, an image obtained by computing acquired measurement data is displayed as a diagnostic image on a display unit associated with the apparatus or on a display unit independent from the apparatus.
An image using a physical property value of living tissue (e.g., T1: longitudinal relaxation time, T2: transverse relaxation time, PD: proton density, D: diffusion coefficient, CT value and the like) as a pixel value is useful in diagnosis of various diseases such as early diagnosis for knee osteoarthritis. Further, such an image is unsusceptible to device parameters derived from hardware and hence, is also useful for clinical researches performed at plural centers.
In the MRI apparatus, for example, RF pulses and gradient magnetic field pulses are applied based on predetermined pulse sequence and imaging parameter, so as to acquire echo signals, based on which an image is formed. At this time, a user can obtain an emphasized image emphasizing relative difference in the physical property of living tissue (e.g., T1: longitudinal relaxation time, T2: transverse relaxation time, PD: proton density, D: diffusion coefficient, and the like) by selecting a pulse sequence. To change the degree of emphasis or the physical property value of an object, the user needs to select another pulse sequence or change the imaging parameter.
It takes much time for the MRI apparatus to make quantitative measurement of the physical property of living tissue. In clinical tests, therefore, an emphasized image generated based on an imaging sequence is commonly used as a diagnostic image. In the diagnosis using such an emphasized image, the diagnosis is made by comparing the signal levels of different types of images. This leads to an increase in the image types and thence, in information volume, which makes diagnosis work cumbersome and complicated. In the case of the MRI apparatus, the emphasized image generated based on the imaging sequence is limited in emphasis pattern. According to a sequence for acquiring a blood vessel image, for example, fat tissue images as well as blood vessel images are simultaneously acquired at high signal levels. This results in post processing involving a clipping operation and the like for removing the fat tissues, which requires much time and an effort of the user.
More recently, on the other hand, there have been proposed a method for high-speed measurement of T1 value or T2 value by using SSFP (Steady State Free Precision) which is a GrE sequence (see, for example, Non-patent Literature 1), and a method of estimating a physical property value as a test subject parameter from a function determined by a numerical simulation (see, for example, Patent Literature 1).